Packaging machines of the shrink wrapping type typically include a first or inlet conveyor section, a cut and seal station, a heat tunnel for shrinking the film that wraps the packages, and a second or outlet conveyor station.
A very popular shrink wrap machine, invented by the present inventor in France about twenty-five years ago, includes a first conveyor means that has plural pivotally mounted sections that can be selectively pivoted so that they project above the plane of the conveyor in preselected patterns. When pivoted upwardly, these section drive the trailing edge of their associated package forwardly through the machine. In the industry, machines of this type have come to be called bucket machines because a package carried by flat, unpivoted sections that is preceded and succeeded by raised or upwardly pivoted sections is said to be in a bucket. The upwardly pivoted sections are often called buckets as well.
Where packages of short longitudinal extent are to be shrink wrapped, every bucket along the extent of the bucket conveyor is pivoted upwardly. Where a package having a longitudinal extent about double that of a short package is to wrapped, every other bucket is pivoted upwardly. Where a package having a longitudinal extent about triple that of a short package is to wrapped, every third bucket is pivoted upwardly, and so on.
Heretofore, the buckets have been pivoted upwardly by manual means. However, there are a number of problems with such manual pivoting of the buckets. First of all, manual pivoting of each bucket is time consuming. Secondly, human error often occurs and the required pattern of lifted buckets may be interrupted, resulting in rejected packages. Moreover, the raised buckets must be manually lowered after the shrink wrapping has taken place. For all of these reasons, a means for automatically raising every bucket, every other bucket, every third bucket and so on is desirable. Moreover, an automatic means for lowering the buckets is equally desirable, but the prior art neither teaches nor suggests how such objects could be achieved.